In a method for manufacturing a flexible display device of a relevant technology, usually, a flexible material is coated on a glass sheet to form a flexible substrate, and then thin film transistors (TFTs) as well as light-emitting elements are fabricated on the flexible substrate. After the manufacture for the display device is finished, flexible components (the flexible substrate, TFTs and the light-emitting elements) are usually separated from the glass sheet using a laser beam. However, the flexible material may not be uniformly coated at a coating beginning region and a coating ending region with respect to other regions, i.e., property of the flexible substrate at a periphery region may be different from that at a central region. Therefore, it is difficult to separate the whole glass sheet from the flexible components using the laser beam, and the flexible components may be damaged during the laser separation process. In view of the above, one solution is to cut off the non-uniform periphery region of the flexible substrate using laser beam before the laser separation process. When cutting the flexible substrate, the glass sheet under the flexible substrate cannot be damaged. Once the glass substrate is damaged, there is a risk of chip breakage in following processes, which affects the overall process yield.